Head-mounted illumination systems are often used by dentists, surgeons, ophthalmologists, etc. when performing examinations and medical procedures since such systems leave the hands free and also project illumination in the same direction the user is looking. Most head-mounted illumination systems use standard flashlight technology (a filament-based lamp with a back reflector). Such illumination systems cannot provide very uniform illumination. Even those systems which use very expensive and precision reflectors have difficulty producing a clean and uniform beam of light. The uniform illumination is not maintained over the long focal range, and these systems produce much stray light.
An ordinary imaging illuminator, using a standard bulb and an imaging lens, has a low collection efficiency and produces a dim light beam. The magnified image of the bulb filament in the illumination plane produces a very uneven light structure.
A uniform, intense illumination area can be produced by using fiber optic illuminators, wherein a very high intensity light source is used with an optical fiber bundle. However, the user must be constantly attached via a tether to the heavy fiber bundle which is, in turn, anchored to an illuminator box that must be plugged into a power outlet. Thus, the mobility and comfort of the wearer is significantly reduced.
What is needed is a compact, portable, lightweight illumination system which may be mounted on the head of a user via a headband, spectacle frames, etc. and which produces intense illumination of a uniform pattern. What is also needed is such an illumination source wherein the spot size of the illumination can quickly and easily be adjusted by the user while maintaining the uniformity of the illumination.